The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. While this process is not without limits, expectations exist of uninterrupted improvement in device scaling, performance, and efficiency. To meet these expectations, new technologies must be aggressively pursued.
Magnetic random access memory (MRAM) is an emerging technology for temporary storage and retrieval of data. Unlike other types of magnetic storage that directly measure magnetic field strength, MRAM data values are determined based on the resistance of a magnetic tunnel junction (MTJ) device within an MRAM cell. The MTJ structure typically comprises two magnetic layers separated by a thin insulator layer. Data is written by altering the magnetic field direction of one of the magnetic layers. This affects the resistance of the structure, thereby storing the written data. Although existing MRAM designs have been generally adequate, they have not proved entirely satisfactory in all respects.